This invention relates generally to an apparatus and method for stabilizing lifting equipment and, more particularly, to an apparatus and method for stabilizing an extendible boom gantry.
One particularly versatile kind of lilting apparatus is the type having an extendible boom supported by vertical extendible boom structures. Such an apparatus, which is exemplified by the extendible gantry lifting apparatus manufactured and distributed by J&R Engineering Company, Inc., of Big Bend, Wis., is described in U.S. patent application Ser. No. 07/971,333 filed Nov. 4, 1992. Such an apparatus provides a machine that can lift large loads to substantial heights and transport them horizontally. In many ways, the versatility of the machine is limited only by the imagination of the operators and riggers who call upon the machine to perform various tasks.
When substantial loads are being raised, safety requires that any potential stability problems be avoided. One possible stability problem can occur when one boom travels farther than another causing misalignments of the extendible booms. Another possible problem can occur when uneven loading or other stresses cause the relationship between the beam and the extendible booms to deviate from perpendicular. Similarly, the extension of two hydraulic cylinders and the operation of two sets of driving wheels must be precisely coordinated. Any such lack of coordination can cause structural failure, particularly when a rigid gantry structure is attached to these mechanisms. Accordingly, means for allowing slight misalignments while retaining the structural integrity of the gantry structure are critically needed.